Headlight-dimmer.



Patented Mar. 13, 1917.

I IN VEN TOR. w/m A! 4% Jam ATTORNEY WITNESS WQQIM unrmn STATES" PATENT OFFICE.

- ALLEN H. BAIBCOCK, OF BERKELEY, CALIFORNIA.

HEADLIGHT-DIMMEB. Y

1 To all whom it may concern:

Be it known that I, ALLEN H. BABGOCK', a citizen of the United States, residing at Berkeley, in the county of Alameda and State of California, have invented certain new and useful Improvements in Headlight- Dimmers, of which the following is a specification.

invention relates to that class of devices for relieving the glare of the headlights of vehicles, in which some form of shield is fitted to the lamp-globe or is asso- Various devices, known as dimmers, have beendeveloped to remove the objectionable features of such headlights, nearly all of which when effective as dimmers,"diminish materially the illuminating powers of the headlights, and, therefore, are detrimental to the safety and the convenience of the driver of the vehicle.

The object of my invention is to remove the objectionable features of such head lights, and at the same time to increase the illumination of the roadway along the path of the vehicle.

- While my invention has been designed to be used in connection with the usual round bulb ainc'andescent electric lights placed withina reflector the surface of which is substantially a paraboloid of revolution,-

and will be described as such, yet it maybe adapted to other forms of illuminant in other forms of'reflectors, as any one skilled in the art can see from the present disclosure.

The nature of my invention, together with the manner of its use and the principles upon which'it is foundedwill be fully asrtained and understood from the followdescription to be read with reference to Specification of Letters Patent. Patented Mar, 13, 1917,

Application filed March 15, 1916. Serial No. 84,268.

the accompanying drawings in which is illustrated one form of its practice.

Figure 1 is a sectional side view of a reflector, with a lamp in the focus thereof, the lamp being in elevation with my dimming reflector member in place.

Fig. 2 is a front elevation of the lamp with attached dimming reflector member.

Fig. 3 is a front elevation of the lamp with a dimming reflector member slightly modified in shape to better adapt it for certain uses.

1 is an electric lamp with its filament 2 wound in concentrated form and placed in a reflector 3, so that the lamp filament is in the focus of the reflector.

When the filament is caused to glow, the

rays of light will issue therefrom in all directions. Those rays that strike the reflector will be reflected along the axis of the reflector and substantially parallel thereto. Those rays that do not strike the reflector will proceed directly from the lamp along radial lines, The direct rays that issue in a downward direction are useful because they strike and illuminate the path of the car between the car and thebrilliantly illuminated area where the reflected rays are directed, and also on each side of the path of the car which is useful in turning curves. On the other hand, the direct rays that issue in an upward direction are objectionable to the driver, particularly in bad weather conditions, such as in fog or in misty weathen, or when it is snowing or raining,

or when dust is rising in the roadway; and

they are objectionable to the drivers of other .vehicles. and to pedestrians, because they tend to confuse the vision by opposing a bright light on a comparatively dark back ground.

4: is a concave spherical reflector of radius substantially that of the lamp-globe 1. The reflector 4 may be associated with the lamp-globe moreor less intimately, that is to say, it may be formed with or'on the globe or adherently attached thereto, or it may be a separate piece,'say 'of metal, with a highly polished inner surface. As a separate piece, it may be supported in any suitable manner. A simple and effective connection is that here shown, namely, a hole 5 in the lower portion, which fits overthe tip of the globe, and a connection, which may be a spring 7, or other link, extending,

' 0116021 each side, from the inner angle of the tionable qualities of the direct rays, enumerated above, be removed, but also those direct rays, so intercepted, will be reflected back toward and focused iaeon the filament 2, and then will proceed from it to the reflector 3, precisely as if they had issued in those directions initially; then they will be reflected forward along the axis, and thus will strengthen the reflected beam; in other words, they will be converted from useless and objectlonable rays to useful rays.

For some uses, such as on locomotive head lights, it has been found desirable to shape the reflector member 4 to intercept some of the direct rays that otherwise would emerge sidewise slightly below the horizontal. This is shown in Fig. 3 in which the sides 4 of said member are dropped slightly below the horizontal plane. In all cases, however, it is best to drop the forward practically one-half the reflected beam. Moreover, no advantage seems consciously or designedly to have been taken of the properties of the spherical reflector torecover and make useful the direct rays so intercepted; and, furthermore, such cups are almost invariably placed on the bottom side of the lamp-globe, so that not only do they fail .to remove 1 the upward objectionable direct rays, but also they do remove the downward useful directrays.

In another very important respect my invention is a distinct improvement. The size of any lamp bulb is determined by the rate of heat radiation necessary to keep the lamp filament within the permissible working temperature and inasmuch as the radiation from unit surface is sensibly constant, the

surface of the'bulb is a direct function of makers designthe bulbs as small as is praclower lip 4" slightly below the horizontal; for two reasons; first, to use the lamp tip";

6 to help support the dimmer, and second, because the lamp filament is not always exe actly central in the lamp globe and always is of appreciable size, consequently some of the direct rays may issue from below the focal point and hence tend to emerge; from the headlight case in directions above the horizontal. In any case, the dimmer should extend overthe upper portion-of the lamp I .globe only asfar back from the front as will insure that none of the direct rays can escape a'round'the edgesof the upper.pe-

riphery of the headlight case.

v Dimmers made according to my above described'invention' have. proven in practice to be useful and'desirable additions to the the dimmers, this opaque mass no longer I 'exists,'because its cause has beenremoved,

and the drivers eye now can follow the 'reticable. If then there is applied to the lamp bulb any device thatlimits the heatradiation therefrom, the temperature of the lamp filament will be increased, and the lamp will deteriorate more rapidly, and its useful life will be materially diminished; also the temperature of a part of the bulb itselfwillbe increased, and such local heating leads to failure of the. glass. Evidently,

then, the dimming member should be as small as possible, and it should be either transparent (which is incompatible with dimming) -or as near as possibletotally refleeting.

' Since all previous forms of cup'dimmers, as far as I am aware, cover one-half, or

nearly one-half of the lamp globe, and are flectingas is commercially practicable, the

distinctive improvement in mydevice isap- ;parent.

In using the term sphericalzherein as up cave face made as highly polished and re- 7 plied to the dimming reflector member, If; do not confine its meaning strictly to a true sphericity, for its curvature may be of conic or other section according to the shape of the lamp-globe; and the term spherical I, therefore, use as generic to any curvature which willreflect back to' the filament of T the lamp.

flected'beam of light to its end. My inven- 1 tion thus tends topromote safety.

I am aware that cups have been applied to headlight lamps, asdimmers'; but they are all, as far as I am aware, hemispherical or nearly so, and, therefore, they cut olf- I claim In a headlight its principal reflector-and its focallamp, a ray-afl'ecting device consisting in its en- 'tirety of a spherical secondary reflector member having a full reflecting surface'on and in combination with, L

its-concave face and an area so related to the principal reflector that none of the direct rays fromthe source of light to the.

principal reflector will be aflected, said member closely co the upper the lamp globe an ing it to principal from the lamp emerge from the vering substantially only forward quadrantal section of d having a radius adaptmtercept and reflect back to the reflector only those direct rays which otherwise. would headlight case aboye the name to this specification in the presence of Witnesses.

twosubscribing ALLEN H. BABGO'CK. Witnesses:

S. CONSTINE, v WM. F. BoorH. 

